The overall goal of this project is to improve the efficacy of transfusion of stored blood. There is good evidence that red blood cell storage results in loss of functionality and integrity of red blood cells over time and that this contributes to deleterious effects upon blood transfusion. This project is built around the hypothesis that this storage lesion is largely due to dysregulation of nitric oxide homeostasis in the blood. This disruption is due to increased nitric oxide scavenging by cell-free hemoglobin and microparticles that are released during hemolysis in stored blood and diminished nitric oxide production by the newly discovered red cell nitric oxide synthase. A vast array of clinical, biophysical, molecular biology, and biochemical tools will be applied to characterize the nitric oxide storage lesion in vitro in stored blood as well as in chimeric mice models, a canine model, and in human studies. In addition, therapeutics will be explored in these systems that could restore nitric oxide homeostasis by reducing nitric oxide scavenging and increasing nitric oxide production. PUBLIC HEALTH RELEVANCE (provided by applicant): There are several potential risks associated with transfusion of stored red blood cells, a procedure performed about 14 million times per year in patients undergoing surgery or with chronic illness. This project explores the hypothesis that deleterious effects of red cell transfusion are due to resulting upset in the availability of the important signaling molecule nitric oxide. The project investigates the cause of this reduction in nitric oxide bioavailability and explores ways to restore nitric oxide upon red cell transfusion.